Once you use EAD, I guess...
1. You don't want to renew your H1B1, but your want to work for the same company. That means you will lose your H1B1.
2. Your switch to another company and you don't want to file H1B1 transfer. You will lose your H1B1.
"我怎麽聽說一旦使用了EDA", as long as you still keep valid H1B1, "使用EDA" will not happen.
Your company is very kind(or your attorney wants to make more money from you). Keep EAD and H1B1 is preferable.